Non-aqueous secondary battery having negative electrode including graphite powder
a secondary battery and graphite powder technology, applied in the field of carbon materials, can solve the problems of affecting the safety of lithium secondary batteries using lithium metal for the negative electrode, affecting the safety affecting the quality of lithium secondary batteries, so as to increase the existing fraction of the hexagonal structure, increase the intercalation-deintercalation capacity of lithium, and reduce the existing fraction of the rhombohedral structur
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embodiment 1
[0050] Flaky natural graphite which was produced from Madagascar was used as the raw material, and the raw material was pulverized to form a powder, of which the particle diameter was equal to or less than 46 μm, using a jet mill. The powder was sieved to obtain a raw material powder. The average diameter of the raw material powder was 8.0 μm. Subsequently, the raw material powder was processed with a heat treatment by heating at 900° C. or 2850° C. for ten days under a nitrogen atmosphere, and the graphite powder of the present invention was obtained.
[0051] The crystalline structures of the graphite powder of the present invention and the raw material powder were analyzed by an X-ray diffraction method using an apparatus RU-200 made by Rigaku Denki, and the impurity content was analyzed by inductively coupled plasma spectrometry (ICP) using an apparatus P-5200 made by Hitachi.
[0052] The X-ray diffraction patterns of the graphite powder of the present invention, which have been ob...
embodiment 2
[0055] In accordance with the embodiment 2, raw graphite was pulverized by a jet mill to less than 100 μm in particle diameter. Then, the graphite powder was immersed into a mixed acid comprised of sulfuric acid and nitric acid for a whole day. Subsequently, washing with distilled water and neutralization with a dilute aqueous solution of sodium hydroxide were performed. The graphite powder obtained by the above process was dried at 120° C. to obtain the graphite powder of the present invention. The X-ray pattern of the graphite powder obtained by the above process is shown in FIG. 5. The peaks at diffraction angles of 43.3 degrees and 46.0 degrees, both of which belong to the rhombohedral structure, are decreased. Accordingly, it was found that the rhombohedral structure was eliminated by the above process.
embodiment 3
[0056] In accordance with the embodiment 3, a carbon electrode was prepared using the graphite powder of the present invention as an electrode active material, and the lithium intercalation-deintercalation capacity, in other words, the load capacity of the negative electrode in the lithium secondary battery, was studied with the electrode.
[0057] Mixed agents slurry were prepared by mixing 90% by weight in total solid of the graphite powder of the present invention prepared in the embodiment 1, 10% by weight of polyvinylidene fluoride (PVDF) as a binder, and N-methyl-2-pyrolidone, of which the heating temperatures were 900° C. and 2850° C., respectively. The mixed agents slurry was applied on a plane of a sheet of copper foil of 10 μm thickness, and dried in a vacuum at 120° C. for one hour. After the vacuum drying, an electrode was fabricated by roller pressing, of which the thickness was in a range of 85-90 μm. The average amount of the applied mixed agents per unit area was 10 mg...
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